The royal penguin found critically unwell on the Wairarapa coast has died overnight.

The juvenile penguin, who was found at Tora on the southern Wairarapa coastline on Sunday had been cared for at The Nest at Wellington Zoo since Monday afternoon.

He was suffering from malnutrition, dehydration and kidney failure after coming ashore to moult while severely underweight.

Veterinary Science manager Lisa Argilla said the zoo did everything they could to give him the best chance of survival.

"As the penguin arrived nearly 3kg underweight it had absolutely no reserves, and subsequently we suspect that this lead to multiple organ failure, following the kidney failure diagnosed on its arrival," she said.

Royal Penguins are normally found on Macquarie Island, more than 2000 kilometers south of where the penguin was spotted on Sunday.

This this was only the fourth confirmed sighting of this species on the North Island of New Zealand.